From the prior art drivetrains for motor vehicles are known which comprise an electric motor, such electric motors are used as drive motors enabling low-emission and almost silent driving, but disadvantageously having only limited drive power. For that reason so-termed hybrid drives have been developed, in which the main power assembly is an internal combustion engine and an electric motor is used as an auxiliary assembly which is arranged in series or in parallel with the drivetrain between the combustion engine and the transmission.
For example, from DE 199 17 665 a hybrid drive for a motor vehicle is known, which comprises in the drivetrain between the combustion engine and the transmission a first electric machine and a second electric machine permanently connected to the transmission input shaft. In this, a shiftable clutch is arranged between the two electric machines, which can each be operated as a motor and a generator, and the combustion engine. This design on the one hand has the advantage that there is no need for electric components such as a starter, generator or pump drive since one of the electric machines can be used as a starter, generator or pump drive. On the other hand, the disadvantage is that two electric machines are needed, and this has a negative effect on manufacturing costs.
Furthermore, from the prior art an arrangement of components of the drivetrain of a motor vehicle is known, which comprises an electric motor and in which, by using an electric motor, other electric components such as a starter, generator etc. can be omitted. In such an arrangement the drivetrain comprises, in the following order, the combustion engine, a clutch, an electric motor, a transmission and an axle gearset, or the combustion engine, a clutch, an electric motor, an input shaft to the transmission, a transmission and an axle gearset.
This arrangement has the added advantage that only one electric motor is needed. For such an arrangement certain applications are also known, such as for example using the electric motor for synchronizing the shifts in a transmission or using the electric motor to assist starting driving and/or maneuvering, the starting drive or maneuvering process being carried out with electric motor support or independently.
In addition, the electric motor can be used to adjust the torque of the clutch characteristic, and for this purpose the transmission is shifted to neutral and the clutch brought to a slipping condition. Then, a defined torque is set at the electric motor. At constant slip the torque at the electric motor corresponds to the transmissible torque at the clutch for the clutch travel point in question. In a further advantageous application of the electric motor, the motor is used to enhance the plausibility of the engine torque of the combustion engine.